Tip-loaded microneedle arrays for transdermal insertion

ABSTRACT

A method of forming a microneedle array can include forming a microneedle array that has one or more bioactive component. The microneedle array can include a base portion and plurality of microneedles extending from the base portion, and the one or more bioactive components are present in a higher concentration in the plurality of microneedles than in the base portion.

RELATED APPLICATIONS

This is the U.S. National Stage of International Application No.PCT/US2013/039084, filed May 1, 2013, which was published in Englishunder PCT Article 21(2), which in turn claims the benefit of U.S.Provisional Application No. 61/641,209, filed May 1, 2012. Theprovisional application is incorporated by reference herein in itsentirety.

ACKNOWLEDGMENT OF GOVERNMENT SUPPORT

This invention was made with government support under grant numbersEB012776, AI076060, and CA121973 awarded by the National Institutes ofHealth. The government has certain rights in the invention.

FIELD

The disclosure pertains to systems and methods for transdermal drugdelivery, and, in particular, to systems and methods for making andusing dissolvable microneedle arrays.

BACKGROUND

The remarkable physical barrier function of the skin poses a significantchallenge to transdermal drug delivery. To address this challenge, avariety of microneedle-array based drug delivery devices have beendeveloped. For example, one conventional method employs solid or hollowmicroneedles arrays with no active component. Such microneedle arrayscan pre-condition the skin by piercing the stratum corneum and the upperlayer of epidermis to enhance percutaneous drug penetration prior totopical application of a biologic-carrier or a traditional patch. Thismethod has been shown to significantly increase the skin's permeability;however, this method provides only limited ability to control the dosageand quantity of delivered drugs or vaccine.

Another conventional method uses solid microneedles that aresurface-coated with a drug. Although this method provides somewhatbetter dosage control, it greatly limits the quantity of drug delivered.This shortcoming has limited the widespread application of this approachand precludes, for example, the simultaneous delivery of optimalquantities of combinations of antigens and/or adjuvant in vaccineapplications.

Another conventional method involves using hollow microneedles attachedto a reservoir of biologics. The syringe needle-type characteristics ofthese arrays can significantly increase the speed and precision ofdelivery, as well as the quantity of the delivered cargo. However,complex fabrication procedures and specialized application settingslimit the applicability of such reservoir-based microneedle arrays.

Yet another conventional method involves using solid microneedle arraysthat are biodegradable and dissolvable. Current fabrication approachesfor dissolvable polymer-based microneedles generally use microcastingprocesses. However, such conventional processes are limited in theactive components that can be embedded into the array and are alsowasteful in that they require that the active components be homogenouslyembedded in the microneedles and their support structures.

Accordingly, although transdermal delivery of biologics usingmicroneedle-array based devices offers attractive theoretical advantagesover prevailing oral and needle-based drug delivery methods,considerable practical limitations exist in the design and fabricationassociated with microneedle arrays constructed using conventionalprocesses.

SUMMARY

The systems and methods disclosed herein include cutaneous deliveryplatforms based on dissolvable microneedle arrays that can provideefficient, precise, and reproducible delivery of biologically activemolecules to human skin. The microneedle array delivery platforms can beused to deliver a broad range of bioactive components to a patient.

The foregoing and other objects, features, and advantages of thedisclosed embodiments will become more apparent from the followingdetailed description, which proceeds with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates exemplary microneedles and their dimensions.

FIG. 2 illustrates an exemplary microneedle array and its dimensions.

FIGS. 3A and 3B illustrate exemplary microneedles with tip-loaded activecomponents.

FIGS. 4A and 4B illustrate exemplary microneedles with tip-loaded activecomponents.

FIGS. 5A and 5B illustrate exemplary microneedles with tip-loaded activecomponents.

FIGS. 6A and 6B illustrate exemplary microneedles with tip-loaded activecomponents.

FIG. 7 illustrates a miniature precision-micromilling system used forfabricating microneedle mastermolds.

FIG. 8 is an SEM image of a micromilled mastermold with pyramidalneedles.

FIG. 9 is an SEM image of a pyramidal production mold.

FIG. 10 is an SEM image of an enlarged segment of the production mold,illustrating a pyramidal needle molding well in the center of the image.

FIGS. 11A-11D illustrate exemplary CMC-solids and embedded activecomponents.

FIGS. 12A-12B illustrate exemplary CMC-solids and embedded activecomponents.

FIG. 13 is a schematic illustration of exemplary vertical multi-layereddeposition structures and methods of fabricating the same.

FIG. 14 is a schematic illustration of exemplary microneedle arraysfabricated using layering and spatial distribution techniques ofembedded active components.

FIG. 15 is a schematic illustration of exemplary microneedle arraysfabricated in a spatially controlled manner.

FIG. 16A is an SEM image of a plurality of pyramidal-type moldedmicroneedles.

FIG. 16B is an SEM image of a single pyramidal-type molded microneedle.

FIG. 17 is an SEM image of a pillar type molded microneedle.

FIG. 18 is a micrograph of pyramidal type molded microneedles.

FIG. 19 is a micrograph of pillar type molded microneedles.

FIG. 20 illustrates various microneedle geometries that can be formedusing micromilled mastermolds or by direct micromilling of a block ofmaterial.

FIG. 21 illustrates a test apparatus for performing failure and piercingtests.

FIG. 22 illustrates force-displacement curves for pillar typemicroneedles (left) and pyramidal type microneedles (right).

FIG. 23 illustrates a finite elements model of microneedle deflectionsfor pillar type microneedles (left) and pyramidal type microneedles(right).

FIG. 24 show various stereo micrographs of the penetration of pyramidal(A, C, E) and pillar (B, D, F) type microneedles in skin explants.

FIGS. 25A, 25B, and 25C illustrate the effectiveness of microneedlearrays in penetrating skin explants.

FIGS. 26A and 26B illustrate in vivo delivery of particulates to theskin draining lymph nodes of microneedle array immunized mice.

FIG. 27 is a bar graph showing immunogenicity of microneedle deliveredmodel antigens.

FIG. 28 is a bar graph showing the stability of the active cargo ofCMC-microneedle arrays in storage.

FIGS. 29A and 29B show induction of apoptosis in epidermal cells thathave been delivered Cytoxan® (cyclophosphamide) through a microneedlearray.

FIG. 30 illustrates a microneedle geometry that can be formed by directmicromilling of a block of material.

FIG. 31 is a stereo microscopic image of a direct-fabricated solidCMC-microneedle array.

FIG. 32 is a stereo microscopic image of a portion of the microneedlearray of FIG. 31.

FIG. 33 is a schematic cross-sectional view of a casting-mold assemblyfor creating a block or sheet of material for direct micromilling.

FIG. 34 is a schematic cross-sectional view of a drying apparatus thatcan be used to dry a block or sheet of material for direct micromilling.

FIG. 35 is a flow cytometry analysis of GFP expressing target 293Tcells.

FIG. 36 illustrates the stability of microneedle embedded viruses aftera number of days in storage.

FIG. 37 illustrates the expression and immunogenicity of microneedlearray delivered adenovectors.

FIG. 38 illustrates an applicator for microneedle insertion into targettissue.

FIG. 39 illustrates applicator head designs for use with the applicatorshown in FIG. 38.

FIG. 40 is a schematic view of dimensional movement of an applicatorhead.

DETAILED DESCRIPTION

The following description is exemplary in nature and is not intended tolimit the scope, applicability, or configuration of the disclosedembodiments in any way. Various changes to the described embodiment maybe made in the function and arrangement of the elements described hereinwithout departing from the scope of the disclosure.

As used in this application and in the claims, the singular forms “a,”“an,” and “the” include the plural forms unless the context clearlydictates otherwise. Additionally, the term “includes” means “comprises.”As used herein, the terms “biologic,” “active component,” “bioactivecomponent,” “bioactive material,” or “cargo” refer to pharmaceuticallyactive agents, such as analgesic agents, anesthetic agents,anti-asthmatic agents, antibiotics, anti-depressant agents,anti-diabetic agents, anti-fungal agents, anti-hypertensive agents,anti-inflammatory agents, anti-neoplastic agents, anxiolytic agents,enzymatically active agents, nucleic acid constructs, immunostimulatingagents, immunosuppressive agents, vaccines, and the like. The bioactivematerial can comprise dissoluble materials, insoluble but dispersiblematerials, natural or formulated macro, micro and nano particulates,and/or mixtures of two or more of dissoluble, dispersible insolublematerials and natural and/or formulated macro, micro and nanoparticulates.

As used herein, the term “pre-formed” means that a structure or elementis made, constructed, and/or formed into a particular shape orconfiguration prior to use. Accordingly, the shape or configuration of apre-formed microneedle array is the shape or configuration of thatmicroneedle array prior to insertion of one or more of the microneedlesof the microneedle array into the patient.

Although the operations of exemplary embodiments of the disclosed methodmay be described in a particular, sequential order for convenientpresentation, it should be understood that disclosed embodiments canencompass an order of operations other than the particular, sequentialorder disclosed. For example, operations described sequentially may insome cases be rearranged or performed concurrently. Further,descriptions and disclosures provided in association with one particularembodiment are not limited to that embodiment, and may be applied to anyembodiment disclosed.

Moreover, for the sake of simplicity, the attached figures may not showthe various ways (readily discernable, based on this disclosure, by oneof ordinary skill in the art) in which the disclosed system, method, andapparatus can be used in combination with other systems, methods, andapparatuses. Additionally, the description sometimes uses terms such as“produce” and “provide” to describe the disclosed method. These termsare high-level abstractions of the actual operations that can beperformed. The actual operations that correspond to these terms can varydepending on the particular implementation and are, based on thisdisclosure, readily discernible by one of ordinary skill in the art.

Tip-Loaded Microneedle Arrays

Dissolvable microneedle arrays enable efficient and safe drug andvaccine delivery to the skin and mucosal surfaces. However, inefficientdrug delivery can result from the homogenous nature of conventionalmicroneedle array fabrication. Although the drugs or other cargo that isto be delivered to the patient are generally incorporated into theentire microneedle array matrix, in practice only the microneedles enterthe skin and therefore, only cargo contained in the volume of theindividual needles is deliverable. Accordingly, the vast majority of thedrugs or other cargo that is localized in the non-needle components(e.g., the supporting structure of the array) is never delivered to thepatient and is generally discarded as waste.

FIGS. 1 and 2 illustrate exemplary dimensions of microneedles andmicroneedle arrays. Based on the illustrative sizes shown in FIGS. 1 and2, a microneedle array that comprises an active component homogenouslydistributed throughout the array exhibits active component waste ofgreater than 40 percent. For example, if the entire area of the array is61 mm² and the microneedle array area is 36 mm², then the percentutilization of the active component is less than 60 percent. Althoughthe dimensions reflected in FIGS. 1 and 2 illustrate a particular sizearray and shape of microneedles, it should be understood that similarwaste is present in any other size microneedle array in which the activecomponent is homogenously distributed throughout the array, regardlessof the size of the array or the shape of the microneedles involved.

The systems and methods described herein provide novel microneedle arrayfabrication technology that utilizes a fully-dissolvable microneedlearray substrate and unique microneedle geometries that enable effectivedelivery of a broad range of active components, including a broad rangeof protein and/or small molecule medicines and vaccines.

As described in more detail herein, in some embodiments, this technologycan also uniquely enable the simultaneous co-delivery of multiplechemically distinct agents for polyfunctional drug delivery. Examples ofthe utility of these devices include, for example, (1) simultaneousdelivery of multiple antigens and adjuvants to generate a polyvalentimmune response relevant to infectious disease prevention and cancertherapy, (2) co-delivery of chemotherapeutic agents, immune stimulators,adjuvants, and antigens to enable simultaneous adjunct tumor therapies,and (3) localized skin delivery of multiple therapeutic agents withoutsystemic exposure for the treatment of a wide variety of skin diseases.

In some embodiments, the systems and method disclosed herein relate to anovel fabrication technology that enables various active components tobe incorporated into the needle tips. Thus, by localizing the activecomponents in this manner, the remainder of the microneedle array volumecan be prepared using less expensive matrix material that is non-activeand generally regarded as safe. The net result is greatly improvedefficiency of drug delivery based on (1) reduced waste ofnon-deliverable active components incorporated into the non-needleportions of the microneedle array, and (2) higher drug concentration inthe skin penetrating needle tips. This technological advance results indramatically improved economic feasibility proportional to the cost ofdrug cargo, and increased effective cargo delivery capacity per needleof these novel microneedle arrays.

FIGS. 3A, 3B, 4A, and 4B illustrate various embodiments of microneedlearrays wherein the active component is concentrated in the microneedletips of the respective arrays. Thus, in contrast to conventionalmicroneedle arrays, the active component is not present at evenconcentration throughout the microneedle array since there is little orno active component present in the supporting base structure. Inaddition, in some embodiments (as shown, for example, in FIGS. 3A, 3B,4A, and 4B), not only is there little or no active component in thesupporting structures, the location of the active component isconcentrated in the upper half of the individual microneedles in thearray.

FIGS. 5A and 5B illustrate exemplary images of microneedles of amicroneedle array that contains active component concentrated in theupper half of the individual microneedles. The active component isillustrated as fluorescent particles that are concentrated in the tip ofthe microneedle, with the tip being defined by an area of themicroneedle that extends from a base portion in a narrowing and/ortapered manner. The base portion, in turn, extends from the supportingstructure of the array.

FIGS. 6A and 6B illustrate additional exemplary images of microneedlesof microneedle arrays that contain active components concentrated in theupper half of the individual microneedles. In FIG. 6A, the activecomponent, which is concentrated in the tip of the microneedles, isBSA-FITC. In FIG. 6B, the active component, which is also concentratedin the tip of the microneedles, is OVA-FITC.

As noted above, in some embodiments, individual microneedles cancomprise active components only in the upper half of the microneedle. Inother embodiments, individual microneedles can comprise activecomponents only in the tips or in a narrowing portion near the tip ofthe microneedle. In still other embodiments, individual needles cancomprise active components throughout the entire microneedle portionthat extends from the supporting structure.

The following embodiments describe various exemplary methods forfabricating microneedle arrays with one or more active componentconcentrated in the upper halves and/or tips of microneedles inrespective microneedle arrays.

Microneedle Arrays Fabricated by Sequential Micro-Molding andSpin-Drying Methods

The following steps describe an exemplary method of fabricatingmicroneedle arrays using sequential micro-molding and spin-drying.Active components/cargo can be prepared at a desired usefulconcentration in a compatible solvent. As described herein, the solventsof the active component(s) can be cargo specific and can comprise abroad range of liquids, including for example, water, organic polar,and/or apolar liquids. Examples of active components are discussed inmore detail below and various information about those active components,including tested and maximum loading capacity of various microneedlearrays are also discussed in more detail below.

If desired, multiple loading cycles can be performed to achieve higheractive cargo loads as necessary for specific applications. In addition,multiple active cargos can be loaded in a single loading cycle as acomplex solution, or as single solutions in multiple cycles (e.g.,repeating the loading cycle described below) as per specificcargo-compatibility requirements of individual cargos. Also, particulatecargos (including those with nano- and micro-sized geometries) can beprepared as suspensions at the desired particle number/volume density.

Example 1

a) As described in more detail below in the micromilling embodiments, anactive cargo's working stock solution/suspension can be applied to thesurface of microneedle array production molds at, for example, about 40μl per cm² surface area.

b) The microneedle array production molds with active cargo(s) can becentrifuged at 4500 rpm for 10 minutes to fill the microneedle arrayproduction molds needles with the working cargo stock.

c) The excess cargo solution/suspension can be removed and the surfaceof the microneedle array production molds, washed with 100 μl phosphatebuffer saline (PBS) per cm² mold-surface area, or with the solvent usedfor the preparation of the active cargo's working stock.

d) The microneedle array production molds containing the active cargostock solution/suspension in the needle's cavity can be spin-dried at3500 rpm for 30 minutes at the required temperature with continuespurging gas flow through the centrifuge at 0-50 L/min to facilitateconcentration of the drying active cargo(s) in the needle-tips. Thepurging gas can be introduced into the centrifuge chamber throughtubular inlets. Moisture content can be reduced using a dehumidifiertempered to the required temperature with recirculation into thecentrifuge chamber. The purging gas can be air, nitrogen, carbon dioxideor another inert or active gas as required for specific cargo(s). Theflow rate is measured by flow-meters and controlled by a circulatingpump device.

e) 100 μl 20% CMC90 hydrogel in H2O can be added to the surfacemicroneedle array production molds' per cm² microneedle array productionmolds-area to load the structural component of the microneedle arraydevice.

f) The microneedle array production molds can be centrifuged at 4500 rpmfor 10 min at the required temperature without purging gas exchange inthe centrifuge chamber to fill up the microneedle array production moldsneedle cavities with the CMC90 hydrogel. This can be followed by a 30min incubation period to enable rehydration of the active cargo(s)previously deposited in the microneedle array tips.

g) The microneedle array production molds can centrifuged at 3500 rpmfor 3 hours or longer at the required temperature with 0-50 L/minconstant purging gas flow through the centrifuge chamber to spin-dry theMNA devices to less than 5% moisture content.

h) The dried microneedle array devices can then be separated from themicroneedle array production molds for storage under the desiredconditions. In some embodiments, CMC90 based devices can be storablebetween about 50° C. to −86° C.

Examples of fabricated tip-loaded active cargo carrying microneedlearrays can be seen in FIGS. 3A-6B.

Micromilled Master Molds and Spin-Molded Microneedle Arrays

In the following embodiments, micromilling steps are preformed to createmicroneedle arrays of various specifications. It should be understood,however, that the following embodiments describe certain details ofmicroneedle array fabrication that can be applicable to processes ofmicroneedle array fabrication that do not involve micromilling steps,including the process described above in the previous example.

In the following embodiments, apparatuses and methods are described forfabricating dissolvable microneedle arrays using master molds formed bymicromilling techniques. For example, microneedle arrays can befabricated based on a mastermold (positive) to production mold(negative) to array (positive) methodology. Micromilling technology canbe used to generate various micro-scale geometries on virtually any typeof material, including metal, polymer, and ceramic parts. Micromilledmastermolds of various shapes and configurations can be effectively usedto generate multiple identical female production molds. The femaleproduction molds can then be used to microcast various microneedlearrays.

FIG. 7 illustrates an example of a precision-micromilling system thatcan be used for fabricating a microneedle mastermold. Mechanicalmicromilling uses micro-scale (for example, as small as 10 μm) millingtools within precision computer controlled miniature machine-toolplatforms. The system can include a microscope to view the surface ofthe workpiece that is being cut by the micro-tool. The micro-tool can berotated at ultra-high speeds (200,000 rpm) to cut the workpiece tocreate the desired shapes. As noted above, the micromilling process canbe used to create complex geometric features with many kinds ofmaterial. Various types of tooling can be used in the micromillingprocess, including, for example, carbide micro-tools. In a preferredembodiment, however, diamond tools can be used to fabricate themicroneedle arrays on the master mold. Diamond tooling can be preferableover other types of tooling because it is harder than conventionalmaterials, such as carbide, and can provide cleaner cuts on the surfaceof the workpiece.

Mastermolds can be micromilled from various materials, including, forexample, Cirlex® (DuPont, Kapton® polyimide), which is the mastermoldmaterial described in the exemplary embodiment. Mastermolds can be usedto fabricate flexible production molds from a suitable material, such asSYLGARD® 184 (Dow Corning), which is the production material describedin the exemplary embodiment below. The mastermold is desirably formed ofa material that is capable of being reused so that a single mastermoldcan be repeatedly used to fabricate a large number of production molds.Similarly each production mold is desirably able to fabricate multiplemicroneedle arrays.

Mastermolds can be created relatively quickly using micromillingtechnology. For example, a mastermold that comprises a 10 mm×10 mm arraywith 100 microneedles can take less than a couple of hours and, in someembodiments, less than about 30 minutes to micromill. Thus, a shortramp-up time enables rapid fabrication of different geometries, whichpermits the rapid development of microneedle arrays and also facilitatesthe experimentation and study of various microneedle parameters.

The mastermold material preferably is able to be cleanly separated fromthe production mold material and preferably is able to withstand anyheighted curing temperatures that may be necessary to cure theproduction mold material. For example, in an illustrated embodiment, thesilicone-based compound SYLGARD® 184 (Dow Corning) is the productionmold material and that material generally requires a curing temperatureof about 80-90 degrees Celsius.

Mastermolds can be created in various sizes. For example, in anexemplary embodiment, a mastermold was created on 1.8 mm thick Cirlex®(DuPont, Kapton® polyimide) and 5.0 mm thick acrylic sheets. Each sheetcan be flattened first by micromilling tools, and the location where themicroneedles are to be created can be raised from the rest of thesurface. Micro-tools can be used in conjunction with a numericallycontrolled micromilling machine (FIG. 1) to create the microneedlefeatures (e.g., as defined by the mastermold). In that manner, themicromilling process can provide full control of the dimensions,sharpness, and spatial distribution of the microneedles.

FIG. 8 is an image from a scanning electron microscope (SEM) showing thestructure of a micromilled mastermold with a plurality of pyramidalneedles. As shown in FIG. 8, a circular groove can be formed around themicroneedle array of the mastermold to produce an annular (for example,circular) wall section in the production mold. The circular wall sectionof the production mold can facilitate the spincasting processesdiscussed below. Although the wall sections illustrated in FIG. 9 andthe respective mastermold structure shown in FIG. 8 is circular, itshould be understood that wall sections or containment means of othergeometries can be provided. For example, depending on what shape isdesired for the microneedle array device, the containment means can beformed in a variety of shapes including, for example, square,rectangular, trapezoidal, polygonal, or various irregular shapes.

As discussed above, the production molds can be made from SYLGARD® 184(Dow Corning), which is a two component clear curable silicone elastomerthat can be mixed at a 10:1 SYLGARD® to curing agent ratio. The mixturecan be degassed for about 10 minutes and poured over the mastermold toform an approximately 8 mm layer, subsequently degassed again for about30 minutes and cured at 85° C. for 45 minutes. After cooling down toroom temperature, the mastermold can be separated from the curedsilicone, and the silicone production mold trimmed to the edge of thecircular wall section that surrounds the array (FIG. 9.). From a singlemastermold, a large number of production molds (e.g., 100 or more) canbe produced with very little, if any, apparent deterioration of theCirlex® or acrylic mastermolds.

FIG. 9 is an SEM image of a pyramidal production mold created asdescribed above. FIG. 10 illustrates an enlarged segment of theproduction mold with a pyramidal needle molding well in the center ofthe image. The molding well is configured to receive a base material(and any components added to the base material) to form microneedleswith an external shape defined by the molding well.

To construct the microneedle arrays, a base material can be used to formportions of each microneedle that have bioactive components and portionsthat do not. As discussed above, each microneedle can comprise bioactivecomponents only in the microneedles, or in some embodiments, only in theupper half of the microneedles, or in other embodiments, only in aportion of the microneedle that tapers near the tip. Thus, to controlthe delivery of the bioactive component(s) and to control the cost ofthe microneedle arrays, each microneedle preferably has a portion with abioactive component and a portion without a bioactive component. In theembodiments described herein, the portion without the bioactivecomponent includes the supporting structure of the microneedle arrayand, in some embodiments, a base portion (e.g., a lower half) of eachmicroneedle in the array.

Various materials can be used as the base material for the microneedlearrays. The structural substrates of biodegradable solid microneedlesmost commonly include poly(lactic-co-glycolic acid) (PLGA) orcarboxymethylcellulose (CMC) based formulations; however, other basescan be used.

CMC is generally preferable to PLGA as the base material of themicroneedle arrays described herein. The PLGA based devices can limitdrug delivery and vaccine applications due to the relatively hightemperature (e.g., 135 degrees Celsius or higher) and vacuum requiredfor fabrication. In contrast, a CMC-based matrix can be formed at roomtemperature in a simple spin-casting and drying process, makingCMC-microneedle arrays more desirable for incorporation of sensitivebiologics, peptides, proteins, nucleic acids, and other variousbioactive components.

CMC-hydrogel can be prepared from low viscosity sodium salt of CMC withor without active components (as described below) in sterile dH₂O. Inthe exemplary embodiment, CMC can be mixed with sterile distilled water(dH₂O) and with the active components to achieve about 25 wt % CMCconcentration. The resulting mixture can be stirred to homogeneity andequilibrated at about 4 degrees Celsius for 24 hours. During thisperiod, the CMC and any other components can be hydrated and a hydrogelcan be formed. The hydrogel can be degassed in a vacuum for about anhour and centrifuged at about 20,000 g for an hour to remove residualmicro-sized air bubbles that might interfere with a spincasting/dryingprocess of the CMC-microneedle arrays. The dry matter content of thehydrogel can be tested by drying a fraction (10 g) of it at 85 degreesCelsius for about 72 hours. The ready-to-use CMC-hydrogel is desirablystored at about 4 degrees Celsius until use.

Active components can be incorporated in a hydrogel of CMC at arelatively high (20-30%) CMC-dry biologics weight ratio before thespin-casting process. Arrays can be spin-cast at room temperature,making the process compatible with the functional stability of astructurally broad range of bioactive components. Since the master andproduction molds can be reusable for a large number of fabricationcycles, the fabrication costs can be greatly reduced. The resultingdehydrated CMC-microneedle arrays are generally stable at roomtemperature or slightly lower temperatures (such as about 4 degreesCelsius), and preserve the activity of the incorporated biologics,facilitating easy, low cost storage and distribution.

In an exemplary embodiment, the surface of the production molds can becovered with about 50 μl (for molds with 11 mm diameter) of CMC-hydrogeland spin-casted by centrifugation at 2,500 g for about 5 minutes. Afterthe initial CMC-hydrogel layer, another 50 μl CMC-hydrogel can belayered over the mold and centrifuged for about 4 hours at 2,500 g. Atthe end of a drying process, the CMC-microneedle arrays can be separatedfrom the molds, trimmed off from excess material at the edges, collectedand stored at about 4 degrees Celsuis. The production molds can becleaned and reused for further casting of microneedle arrays.

In some embodiments, CMC-solids can be formed with layers that do notcontain active components and layers that contain active components.FIGS. 11A-D illustrate CMC-solids with different shapes (FIGS. 11A and11B) and embedded active cargos on an upper layer which becomes, aftermicromilling, the portions of the microneedle with the activecomponents. FIG. 11C illustrates micron sized fluorescent particleslayered on a surface of a non-active component containing layer and FIG.11D illustrates toluidine blue examples layered on a surface of anon-active component containing layer.

FIGS. 12A and 12B also illustrate CMC-solids with different shapes, withFIG. 12B showing a square shape and FIG. 12B showing a rectangularshape. Both CMC solids can be milled to dimensions for furtherprocessing as described herein. It should be understood that thegeometries and the active cargo shown herein are not intended to belimited to the exemplary embodiments.

Example 2

CMC-solids can be prepared with defined geometry and active cargocontents in one or more layers of the prepared structure. Examples ofactive cargos integrated into CMC-solids are described more detailherein. Upon construction of the CMC-solids with embedded active cargocontained in at least one layer of the CMC-solid, the CMC solids can bemilled to project-specific dimensions and micro-milled to fabricatemicroneedle devices as described herein.

Example 3

In another embodiment, one or more layers of active cargo can beembedded on CMC-solids for direct micromilling of the microneedle array.FIG. 13 illustrates a sample representation of vertical multi-layereddeposition and CMC embedding of active cargos on CMC-solids for directmicro-milling of MNA devices.

In one exemplary method, microneedle arrays can be fabricated bypreparing CMC-solids with a defined geometries and without any activecargo contained therein. Then, blank CMC-solids can be milled to adesired dimension.

As shown in FIG. 13, active cargo(s) can be deposited onto the CMC-solidin project specific geometric patterns for inclusion of the activecargo(s) specifically in the tips of micro-milled MNA devices.

The methods active cargo deposition onto the CMC-solid blank caninclude, for example:

1) Direct printing with micro-nozzle aided droplet deposition.

2) Transfer from preprinted matrices.

3) Droplet-deposition with computer controlled robotic systems.

FIG. 14 illustrates layering and spatial distribution of embedded activecargos in a CMC-solid block. After the first layer is deposited (A) itcan be covered with a CMC layer (B) that provides the surface for thesubsequent deposition of the active cargo (C). The process can berepeated until all desired layers are deposited and encased in a solidCMC-block suitable for the micro-milling process (D-F).

FIG. 15 illustrates a schematic view of a cross-section of a CMC-blockencasing the deposits of the active cargo in a spatially controlledmanner (A). The method allows 3-dimensional control and placement of theactive components after micro-milling in the MNA-device (B). In panel(B) of FIG. 15, the placement of the active cargos are shown in thestems of the active cargo; however through the control of the millingprocess the placement can be controlled vertically from the tip to thebase of the microneedles. Colors represent different active componentsor different amount/concentration of the same material.

Thus, a method of vertically layered deposition of active cargos inmicroneedles is provided by depositing one or more active cargossequentially on the surface of the CMC-solids in contact with each otheror separated by layers of CMC. In some embodiments, horizontal patterndeposition of the active cargos can result in spatial separation of thecargos. By combining vertical and horizontal patterning of active cargodeposition, 3 dimensional delivery and distribution of each of thedefined active components can be achieved, further reducing waste ofactive components during fabrication of microneedle arrays.

Microneedle Integrated Adenovectors

The following embodiments are directed to dissolvable microneedlearrays, such as those described herein, that incorporate infectiousviral vectors into the dissolvable matrix of microneedle arrays. Usingthis technology, for the first time, living viral vectors can beincorporated into microneedle arrays. As described herein, theincorporation of viral vectors within the disclosed microneedle arraysstabilizes the viral vectors so that they maintain their infectivityafter incorporation and after prolonged periods of storage. Theapplication of microneedle array incorporated adenovectors (MIAs) to theskin results in transfection of skin cells. In a vaccine setting, wehave demonstrated that skin application of MIAs encoding an HIV antigenresults in potent HIV specific immune responses. These results aredescribed in detail in the examples below.

Example 4

The microneedle integrated adenovectors preparation method describedherein preserves the viability of the adenoviral particles during thepreparation and in dry storage. These steps were specifically designedbased on the physical and chemical properties of CMC microneedle arrays.Viral viability in CMC microneedle arrays was achieved by

-   -   Inclusion of low viscosity carboxymethyl cellulose (CMC90) at        2.5% final concentration (step 2.) and by    -   Timed and temperature controlled spin-drying concentration of        the adenoviral particles in the tips of the microneedle array        devices (step 6.).    -   Controlled partial rehydration of the needle-tip loaded        adenoviral particles (step 8.)

Preparation of Tip-Loaded Microneedle Integrated Adenovectors (MIAs):

1) Resuspend adenoviral particles at 2×109 particles/ml density inTrehalose-storage buffer (5% trehalose Sigma-Aldrich USA, 20 mM TrispH7.8, 75 mM NaCl, 2 mM MgCl2, 0.025% Tween 80)

2) Mix resuspended viral stock with equal volume of 5% CMC90 prepared inTrehasole-storage buffer, resulting in a 1×109 particles/ml densityadenoviral working stock.

3) Add adenoviral working stock suspension to the surface of microneedlearray production molds (as described in detail in other embodimentsherein) at 40 μl per cm2 surface area.

4) The molds are centrifuged at 4500 rpm for 10 minutes at 22° C. tofill the needle tips with adenoviral working stock.

5) The excess viral stock is removed and the surface of the molds washedwith 100 μl (phosphate buffer saline (PBS) solution per cm2 mold-surfacearea.

6) The microneedle array-molds containing the adenoviral stock solutiononly in the needle's cavity are partially spin-dried at 3500 rpm for 10minutes at 22° C.

7) 100 μl 20% structural, non-cargo containing CMC90 hydrogel in H2Oadded to the surface microneedle array-molds' per cm2 mold-area to formthe structure of the MIA device.

8) Centrifuge at 4500 rpm for 10 min at 22° C. to fill up the needlecavities with 20% CMC90 and allow 30 min incubation for the rehydrationof the adenoviral particles dried in the tips (step 3-6, above).

9) By centrifugation spin-dry the MIA devices to less than 5% moisturecontent at 3500 rpm for 3 hours at 22° C. with 10 L/min constant airflow through the centrifuge chamber.

10) De-mold the dried MIA devices for storage at 4° C. or −80° C.

Example 5

We have evaluated the potency and stability MNA incorporated recombinantadenoviral particles. Ad5.EGFP was incorporated into CMC hydrogel MNAsto fabricate a final product that contained 1010 virus particles/MNA.Control blank MNAs were prepared identically but without the virus.Batches of Ad5.EGFP and control MNAs were stored at RT, 4° C. and at−86° C. and viral stability was evaluated in infectious assays. Specifictransduction activity of the MNA incorporated Ad5.EGFP virus wasassessed in vitro using 293T cells. Cells were plated at 2×106/well insix well plates and transduced in duplicate with diluted virussuspension, suspension+empty MNA (control), or Ad5.EGFP MNAs stored atRT, 4° C. and −86° C. for the indicated time periods. As a negativecontrol untransduced wells were included. Initially cell populationswere analyzed after 24 h by flow cytometry for GFP expression(representative histogram is shown in FIG. 35.).

As shown in FIG. 35, the incorporation of Ad5.EGFP into MNAs does notreduce transduction efficiency. Flow cytometry analysis of GFPexpressing target 293T cells 24 h after transduction with identicaltiters of Ad5.EGFP either in suspension or incorporated into CMC-patchesvs. untransfected control cells. FIG. 36 shows the stability of MNAembedded Ad5.EGFP virus. GFP gene expression was assayed by flowcytometry as in FIG. 37 and normalized to the infection efficiency of−86° C. preserved Ad5.EGFP suspension.

It has been found that the infection efficiency using MNA Ad5.EGFP viruswas 87.92±4.5%, which is similar to that observed for traditional −86°C. preserved Ad5.EGFP suspension (FIGS. 35 and 36), suggesting that themanufacturing process does not adversely affect the transductionefficiency of Ad-EGFP viral particles. To asses infectivity over time,the transfection efficiency of freshly prepared −86° C. preservedAd5.EGFP suspensions was compared to that of MNA incorporated Ad5.EGFPstored for prolonged periods of time at either RT, 4 C, or −86 C.Infectivity (normalized to Ad5.EGFP suspension+empty CMC-patch) isreported for storage periods of up to 365 days (FIG. 36). These resultssuggest that the infectiousness of MNA Ad5.EGFP is remarkably stablewith storage at either 4 C or −86 C, and somewhat stable at RT for up to30 days.

These results demonstrate that microneedle array delivered Ad transgenesare expressed in the skin and induce potent cellular immune responses.To specifically evaluate gene expression in vivo, we determined GFPexpression in skin following either traditional intradermal injection(I.D.) or microneedle array-mediated intracutaneous delivery. Wedelivered 108 Ad5.GFP viral particles by ID injection or topically via asingle microneedle array application (FIG. 37). Skin was harvested 48 hlater, cryosectioned, counter-stained using blue fluorescent DAPI toidentify cell nuclei, and then imaged by fluorescent microscopy.Significant cellular GFP expression was observed following both I.D. andmicroneedle array delivery. To evaluate immunogenicity, we evaluatedantigen-specific lytic activity in vivo following a single I.D. ormicroneedle array immunization without boosting. For this purpose weimmunized groups of mice with E1/E3-deleted Ad5-based vectors thatencode codon-optimized SIVmac239 gag full-length or SIVmac239 gag p17antigens (Ad5.SIV gag, Ad5.SIV gag p17). Empty vector was used as acontrol (Ad5). We observed potent and similar levels of in vivo lyticactivity specific for the dominant SIVgag p17-derived peptide KSLYNTVCV(SIVmac239 gag 76-84) following either I.D. or microneedle arrayimmunization with either Ad5.SIV gag or Ad5.SIV gag p17 (FIG. 37, CTL).

The microneedle array technology disclosed herein can also facilitateclinical gene therapy. It addresses, for example, at least two majorlimitations of conventional approaches. First, it enables stabilizationand storage of recombinant viral vectors for prolonged periods of time.By rendering live virus vectors resistant to high and low temperatureswith proven seroequivalence to frozen liquid formulations, microneedlearray stabilization will relieve pressures related to the ‘cold chain.’Further, integration in microneedle arrays enables precise, consistentand reproducible dosing of viral vectors not achievable by conventionalmethods. Finally, the viral vector is repackaged in the only necessarydelivery device, the biocompatible and completely disposable microneedlearray that directs delivery precisely to the superficial layers of theskin.

Such a gene delivery platform is useful in providing patient-friendly,clinical gene therapy. Since these microneedle arrays have beenengineered to not penetrate to the depth of vascular or neuralstructures, gene delivery to human skin will be both painless andbloodless. In addition, the fabrication process is flexible, enablingsimple and rapid low cost production with efficient scale-up potential.Also, as a final product, the MIA device it is stable at roomtemperature and is inexpensive to transport and store. In combination,these structural and manufacturing advantages can enable broad and rapidclinical deployment, making this gene delivery technology readilyapplicable to the prevention and/or treatment of a broad range of humandiseases. Moreover, this approach can be extended to other vector-basedvaccine platforms that are currently restricted by the same limitations(e.g., vaccinia virus, AAV etc.). For at least these reasons, thedisclosed microneedle arrays and methods of using the same significantlyadvance the recombinant gene therapy field.

Microneedle Arrays—Exemplary Active Components

Various active components are described in detail below. Forconvenience, the following examples are based on an microneedle arraywhich is 6.3×6.3 mm. This size, and hence cargo delivery can be variedby increasing or decreasing 2-100 fold.

General considerations for the maximum active cargo quantities include,for example, total needle volume in the array and solubility of theactive component(s) in the solvent (generally expected to be <50%).

Amount Tip Loaded into MNA device μg/device Tip Loaded (unless indicatedMax. predicted Components: differently) loading capacity Live viruses⁽¹⁾Ad5.GFP (adeno viral 5 × 10⁸ 2-5 × 10⁹ GFP expression vector)particles/MNA particles/MNA Ad-SIVgag (adeno viral 5 × 10⁸ 2-5 × 10⁹ gagexpression vector) particles/MNA particles/MNA Ad-SIVp17 (adeno viral 5× 10⁸ 2-5 × 10⁹ gag-p17 expression vector) particles/MNA particles/MNAΨ5 (non-recombinant 5 × 10⁸ 2-5 × 10⁹ Ad vector) particles/MNAparticles/MNA Lenti-GFP⁽²⁾ (Lenti viral 5 × 10⁶ 2-5 × 10⁷ GFP expressionvector) particles/MNA particles/MNAVaccinia virus (immunization)Recombinant vaccinia virus (gene therapy, genetic engineering)Seasonal influenzaMMR (Measles, Mumps, Rubella)

Proteins/Peptides BSA (FITC labeled) 240 400 OVA (FITC labeled) 100 400OVA (no label) 240 400 Flu (split vaccine) 0.22 (2-5) EpitopePeptides⁽³⁾ TRP-2 50 200 EphA2 (a) 50 400 EphA2 (b) 50 400 DLK-1 50 200Multiple epitopes 200 400-600 in one MNA Substance-P 15 (NK-1R ligand)Nucleic acids CpG 1668 120 250 CpG 2006 120 250 Poly(I:C) 250 250Plasmid vectors 100 200 (High mol. weight DNA) Peptides/Nucleic acidcombos OVA/CpG 250/120 OVA/CpG/poly(I:C) 250/120/250 Epitope 200/250peptides/poly(I:C) Organics Doxorubicin 100 R848 (TLR7/8 ligand) 6 L7332 (NK-1 antagonist) DNCB (irritant) 100 Particulates Micro-particles 1 ×10⁶ 2-5 × 10⁷ (1 μ diameter particles/MNA particles/MNA microsphares)Nano Scale ParticlesPLG/PLA Based

Other Biologic tumor lysate/CpG 250/120 tumor lysate/CpG/poly(I:C)250/120/250 tumor lysates/poly(I:C) 200/250Tip-loading of live adenoviruses generally includes the followingmodifications:

a) The presence of 5% trehalose and 2.5% CMC90 in the tip-loadinghydrogel suspension.

b) The temperature of the process is maintained at 22° C.

In addition, Lenti viral vectors generally require 4° C. processing andvapor trap based humidity controls. Also, short epitope peptidesgenerally are solubilized in DMSO, with the evaporation time of thesolvent during tip-loading is 4 hours.

Microneedle Structures and Shapes

For each of the embodiments below, it should be understood that one ormore layers of active components can be provided in the microneedles ofthe microneedle arrays as described above. Thus, for example, in someembodiments, active components are only provided in the area of themicroneedle—not in the structural support of the array, such as shown inFIG. 15. Moreover, in other embodiments, the active components areconcentrated in the upper half of the microneedles, such as in the tipsof the microneedles as shown in FIGS. 3A-4B.

FIGS. 16A and 16B are SEM images of a CMC-microneedle array formed witha plurality of pyramidal projections (i.e., microneedles). The averagetip diameter of the pyramidal needles shown in FIG. 16A is about 5-10μm. As shown in FIG. 16B, the sides of the pyramidal needles can beformed with curved and/or arcuate faces that can facilitate insertion inskin.

FIG. 17 is another SEM image of a single needle of a microneedle array.The microneedle shown in FIG. 17 is a base-extended pillar type moldedCMC-microneedle. The base-extended pillar type microneedle comprises abase portion, which is generally polyagonal (for example, rectangular)in cross section, and a projecting portion that extends from the baseportion. The projecting portion has a lower portion that issubstantially rectangular and tip portion that generally tapers to apoint. The tip portion is generally pyramidal in shape, and the exposedfaces of the pyramid can be either flat or arcuate. The projectingportion can be half or more the entire length of the needle.

FIGS. 18 and 19 illustrate micrographs of pyramidal (FIG. 18) and pillartype (FIG. 19) molded CMC-microneedles. Because the pyramidal needleshave a continually increasing cross-sectional profile (dimension) fromthe needle point to the needle base, as the needle enters the skin, theforce required to continue pushing the pyramidal needle into the skinincreases. In contrast, pillar type needles have a generally continuouscross-sectional profile (dimension) once the generally rectangularportion of the projection portion is reached. Thus, pillar type needlescan be preferable over pyramidal type needles because they can allow forthe introduction of the needle into the skin with less force.

FIG. 20 illustrates schematic representation of microneedle shapes andstructures that are generally suitable for fabrication by spin-castingmaterial into a mastermold formed by micromilling. Since the shapes andstructures shown in FIG. 20 do not contain any undercuts, they generallywill not interfere with the molding/de-molding process. The structuresin FIG. 20 include (a) a generally pyramidal microneedle, (b) a “sharp”pillar type microneedle (without the base member of FIG. 8), (c) a“wide” pillar type microneedle, (d) a “short” pillar type microneedle(having a short pillar section and a longer pointed section), and (e) a“filleted” pillar type microneedle.

While the volume of the pyramidal microneedles can be greater than thatof the pillar type microneedles, their increasing cross-sectionalprofile (dimension) requires an increasing insertion force. Accordingly,the geometry of the pyramidal microneedles can result in reducedinsertion depths and a reduced effective delivery volume. On the otherhand, the smaller cross-sectional area and larger aspect ratio of thepillar microneedles may cause the failure force limit to be lower. Thesmaller the apex angle α, the “sharper” the tip of the microneedle.However, by making the apex angle too small (e.g., below about 30degrees), the resulting microneedle volume and mechanical strength maybe reduced to an undesirable level.

The penetration force of a microneedle is inversely proportional to themicroneedle sharpness, which is characterized not only by the included(apex) angle of the microneedles, but also by the radius of themicroneedle tip. While the apex angle is prescribed by the mastermoldgeometry, the tip sharpness also depends on the reliability of the mold.Micromilling of mastermolds as described herein allows for increasedaccuracy in mold geometry which, in turn, results in an increasedaccuracy and reliability in the resulting production mold and themicroneedle array formed by the production mold.

The increased accuracy of micromilling permits more accurate anddetailed elements to be included in the mold design. For example, asdiscussed in the next section below, the formation of a fillet at thebase of a pillar type microneedle can significantly increase thestructural integrity of the microneedle, which reduces the likelihoodthat the microneedle will fail or break when it impacts the skin. Whilethese fillets can significantly increase the strength of themicroneedles, they do not interfere with the functional requirements ofthe microneedles (e.g., penetration depth and biologics volume). Suchfillets are very small features that can be difficult to create in amaster mold formed by conventional techniques. However, the micromillingtechniques described above permit the inclusion of such small featureswith little or no difficulty.

Mechanical Integrity and Penetration Capabilities

Microneedle arrays are preferably configured to penetrate the stratumcorneum to deliver their cargo (e.g., biologics or bioactive components)to the epidermis and/or dermis, while minimizing pain and bleeding bypreventing penetration to deeper layers that may contain nerve endingsand vessels. To assess the mechanical viability of the fabricatedmicroneedle arrays, tests were performed on the pyramidal and pillartype microneedle arrays as representative variants of array geometry(shown, e.g., in FIGS. 7B and 8). The first set of tests illustrate thefailure limit of microneedles, and include pressing the microneedlearray against a solid acrylic surface with a constant approach speed,while simultaneously measuring the force and the displacement untilfailure occurs. The second set of tests illustrate the piercingcapability of the microneedles on human skin explants.

FIG. 21 illustrates a test apparatus designed for functional testing.The sample (i.e., microneedle array) was attached to a fixture, whichwas advanced toward a stationary acrylic artifact (PMMA surface) at aconstant speed of about 10 mm/s speed using a computer-controlled motionstage (ES14283-52 Aerotech, Inc.). A tri-axial dynamometer (9256C1,Kistler, Inc.) that hosted the acrylic artifact enabled high-sensitivitymeasurement of the forces.

FIG. 22 illustrates force-displacement curves of data measured duringfailure tests. The curve on the left is representative of data obtainedfrom testing a pillar microneedle sample and the curve on the right isrepresentative of data obtained from testing a pyramid microneedle. Asseen in FIG. 22, the failure of these two kinds of microneedles aresignificantly different; while the pyramidal arrays plastically deform(bend), the pillar type arrays exhibit breakage of the pillars at theirbase. This different failure behavior lends itself to considerablydifferent displacement-force data. The failure (breakage) event can beeasily identified from the displacement-force data as indicated in thefigure. Based on the obtained data, the failure point of pillar typemicroneedles was seen to be 100 mN in average. As only about 40 mN offorce is required for penetration through the stratum corneum, themicroneedles are strong enough to penetrate human skin without failure.Furthermore, since parallelism between microneedle tips and the acrylicartifact cannot be established perfectly, the actual failure limit willlikely be significantly higher than 100 mN (i.e., microneedles broke ina successive manner, rather than simultaneous breakage of most/allmicroneedles).

The pyramidal microneedles presented a continuously increasing forcesignature with no clear indication of point of failure. To identify thefailure limit for the pyramidal microneedles, interrupted tests wereconducted in which the microneedles were advanced into the artifact by acertain amount, and retreated and examined through optical microscopeimages. This process was continued until failure was observed. For thispurpose, the failure was defined as the bending of the pyramidalmicroneedles beyond 15 degrees.

To further analyze the failure of the microneedles, the finite-elementsmodel (FEM) of the microneedle arrays shown in FIG. 23 was developed. Toobtain the mechanical properties (elastic modulus and strength limit) ofthe CMC material, a series of nanoindentation tests (using a Hysitronnanoindentor). The average elastic modulus and yield strength of the CMCmaterial (as prepared) were 10.8 GPa and 173 MPa, respectively. Thisindicates that the prepared CMC material has a higher elastic modulusand yield strength than both PMMA (elastic modulus: 3.1 GPa, yieldstrength: 103 MPa) and polycarbonate (elastic modulus: 2.2 GPa, yieldstrength: 75 MPa), indicating the superior strength and stiffness of CMCmaterial with respect to other polymers.

Using this data, a series of FEM simulations were conducted. It waspredicted from the FEM models that failure limit of pyramidal andsharp-pillar (width=134 μm) microneedles with 600 μm height, 30 degreeapex angle, and 20 μm fillet radius were 400 mN (pyramid) and 290 mN(sharp-pillar) for asymmetric loading (5 degrees loadingmisorientation). Considering that the minimum piercing force requirementis about 40 mN, pyramid and sharp-pillar microneedles would have factorsof safety of about 10 and 7.25, respectively.

When the fillet radius is doubled to 40 μm, the failure load for thepillar was increased to 350 mN, and when the fillet radius is reduced to5 μm, the failure load was reduced to 160 mN, which is close to theexperimentally determined failure load. The height and width of thepillars had a significant effect on failure load. For instance, for 100μm width pillars, increasing the height from 500 μm to 1000 μm reducedthe failure load from 230 mN to 150 mN. When the width is reduced to 75μm, for a 750 μm high pillar, the failure load was seen to be 87 mN.

To evaluate penetration capability, pyramidal and sharp-pillarmicroneedle arrays were tested for piercing on water-based model elasticsubstrates and on full thickness human skin. FIG. 24 illustrates stereomicrographs of pyramidal (Panels A, C, and E) and pillar typemicroneedle arrays (B, D, and F) after 4 minutes of exposure to modelelastics. In particular, toluene blue tracer dye was deposited in modelelastic substrates (Panels C and D) or freshly excised full thicknesshuman skin explants (Panels E and F) after application of pyramidal orpillar type microneedle arrays.

The model elastic substrate comprised about 10% CMC and about 10%porcine gelatin in PBS gelled at about 4 degrees Celsius for about 24hours or longer. The surface of the elastics was covered with about 100μm thick parafilm to prevent the immediate contact of the needle-tipsand the patch materials with the water based model elastics. To enablestereo microscopic-imaging, trypan blue tracer dye (Sigma Chem., cat#T6146) was incorporated into the CMC-hydrogel at 0.1% concentration.The patches were applied using a spring-loaded applicator and analyzedafter about a 4 minute exposure. Based on physical observation of thedye in the target substrates, the dissolution of the microneedles of thetwo different geometries was markedly different.

The sharp-pillar needles applied to the model elastic substrate releasedsubstantially more tracer dye to the gel matrix than that observed forthe pyramidal design (FIG. 24, C vs. D). Images of the recovered patches(FIG. 24, A vs. B) were consistent with this observation, as thedegradation of the sharp-pillar needles was more advanced than that ofthe pyramidal needles. To extrapolate this analysis to a more clinicallyrelevant model, pyramidal and pillar type microneedle arrays wereapplied to freshly excised full thickness human skin explants using thesame force from the spring loaded applicator. Consistent with resultsfrom the elastic model, the pyramidal microneedle arrays depositedvisibly less tracer dye than the sharp-pillar microneedle arrays (FIG.24, E vs. F).

To further evaluate penetration and to assess delivery effectiveness tohuman skin, CMC-microneedle arrays were fabricated with BioMag(Polysciences, Inc., cat#. 84100) beads or fluorescent particulatetracers (Fluoresbrite YG 1 μm, Polysciences Inc., cat#. 15702). Thepyramidal CMC-microneedle arrays containing fluorescent or solidparticulates were applied to living human skin explants as describedpreviously. Five minutes after the application, surface residues wereremoved and skin samples were cryo-sectioned and then counterstainedwith toluene blue for imaging by light microscopy (FIGS. 25A and 25B) orby fluorescent microscopy (FIG. 25C).

Pyramidal CMC-microneedles effectively penetrated the stratum corneum,epidermis, and dermis of living human skin explants, as evidenced by thedeposition of Biomag beads lining penetration cavities corresponding toindividual needle insertion points (representative sections shown inFIGS. 25A and 25B). In particular, ordered cavities (FIG. 25A, cavitiesnumbered 1-4, toluene blue counterstain, 10×) and deposits of BioMagparticles (brown) lining penetration cavities were evident (FIG. 25B,40×), indicating microneedle penetrated of human skin. Further, analysisof sections from living human explants stained with DAPI to identifycell nuclei and anti-HLA-DR to identify MHC class II+ antigen presentingcells revealed high density fluorescent particulates deposited in thesuperficial epidermis and dermis, including several particlesco-localized with class II+ antigen presenting cells (FIG. 25C, DAPI(blue), HLA-DR+ (red) and fluorescent particles (green), 40×).

These results further demonstrate that the CMC microneedle arraysdescribed herein can effectively penetrate human skin and deliverintegral cargo (bioactive components), including insoluble particulates.They are consistent with effective delivery of particulate antigens toantigen presenting cells in human skin, currently a major goal ofrational vaccine design.

To further address microneedle array delivery in vivo, the cutaneousdelivery of particulate antigen in vivo was modeled by similarlyapplying fluorescent particle containing arrays to the dorsal aspect ofthe ears of anesthetized mice. After 5 minutes, patches were removed andmice resumed their normal activity. Three hours or 3 days, ear skin anddraining lymph nodes were analyzed for the presence of fluorescentparticles. Consistent with observations of human skin, particulates wereevident in the skin excised from the array application site (data notshown). Further, at the 3 day time point, substantial numbers ofparticles were evident in the draining lymph nodes. FIGS. 26A and 26Billustrates substantial numbers of particles that were evident in thedraining lymph Nodes (FIG. 26A, 10×), including clusters of particulatesclosely associated with Class II+ cells (FIG. 26B, 60×) suggesting thepresence of lymph node resident antigen presenting cells withinternalized particulates.

To quantitatively evaluate the effects of needle geometry on cargodelivery using microneedle arrays, 3H-tracer labeled CMC-microneedlearrays were constructed. The CMC-hydrogel was prepared with 5% wtovalbumin as a model active component at 25 wt % final dry weightcontent (5 g/95 g OVA/CMC) and trace labeled with 0.1 wt % trypan blueand 0.5×106 dpm/mg dry weight 3H-tracer in the form of 3H-thymidine (ICNInc., cat #2406005). From a single batch of labeledCMC-hydrogel-preparation four batches of 3H-CMC-microneedle arrays werefabricated, containing several individual patches of pyramidal andsharp-pillar needle geometry. The patches were applied to human skinexplants as described above and removed after 30 min exposure. Thepatch-treated area was tape-striped to remove surface debris and cutusing a 10 mm biopsy punch. The 3H content of the excised human skinexplants-discs was determined by scintillation counting. The specificactivity of the 3H-CMC-microneedle patch-material was determined andcalculated to be 72,372 cpm/mg dry weight. This specific activity wasused to indirectly determine the amount of ovalbumin delivered to andretained in the skin. The resulting data is summarized in Table 1 below.

The tested types of patches were consistent from microneedle array tomicroneedle array (average standard deviation 24-35%) and batch to batch(average standard deviation 7-19%). The intra-batch variability for bothneedle geometry was lower than the in-batch value indicating that theinsertion process and the characteristics of the target likely plays aprimary role in the successful transdermal material delivery andretention. The patch-material retention data clearly demonstrate theforemost importance of the microneedle geometry in transdermal cargodelivery. Pillar-type needle geometry afforded an overall 3.89 foldgreater deposition of the 3H labeled needle material than that of thepyramidal needles. On the basis of the deposited radioactive material,it is estimated that the pyramidal needles were inserted about 200 μmdeep while the pillar-type were inserted about 400 μm or more.

TABLE 4.2.5 Transfer of ³H-labeled CMC-microneedle material into humanskin explants by pyramidal and pillar-type needles. Pyramid PyramidalNeedles Pillar-Type Pillar-Type Needles Pillar to Array Needles STDevOVA Transferred Needles STDev OVA Transferred Pyramid Batches(cpm/patch) (%) (μg/patch) (cpm/patch) (%) (μg/patch) Ratio Batch A2459.00 17.56 1.70 11700.50 31.52 8.08 4.76 Batch B 3273.50 57.39 2.2612816.50 21.45 8.85 3.92 Batch C 2757.75 46.13 1.90 12240.00 26.77 8.464.44 Batch D 3782.00 36.27 2.61 10921.50 9.32 7.55 2.89 IntraBatch3068.06 19.00 2.12 11919.63 6.77 8.24 3.89 AVG

Desirably, the microneedle arrays described herein can be used forcutaneous immunization. The development of strategies for effectivedelivery of antigens and adjuvants is a major goal of vaccine design,and immunization strategies targeting cutaneous dendritic cells havevarious advantages over traditional vaccines.

The microneedle arrays described herein can also be effective inchemotherapy and immunochemotherapy applications. Effective and specificdelivery of chemotherapeutic agents to tumors, including skin tumors isa major goal of modern tumor therapy. However, systemic delivery ofchemotherapeutic agents is limited by multiple well-establishedtoxicities. In the case of cutaneous tumors, including skin derivedtumors (such as basal cell, squamous cell, Merkel cell, and melanomas)and tumors metastatic to skin (such as breast cancer, melanoma), topicaldelivery can be effective. Current methods of topical delivery generallyrequire the application of creams or repeated local injections. Theeffectiveness of these approaches is currently limited by limitedpenetration of active agents into the skin, non-specificity, andunwanted side effects.

The microneedle arrays of the present disclosure can be used as analternative to or in addition to traditional topical chemotherapyapproaches. The microneedle arrays of the present disclosure canpenetrate the outer layers of the skin and effectively deliver theactive biologic to living cells in the dermis and epidermis. Delivery ofa chemotherapeutic agents results in the apoptosis and death of skincells.

Further, multiple bioactive agents can be delivered in a singlemicroneedle array (patch). This enables an immunochemotherapeuticapproach based on the co-delivery of a cytotoxic agent with and immunestimulant (adjuvants). In an immunogenic environment created by theadjuvant, tumor antigens releases from dying tumor cells will bepresented to the immune system, inducing a local and systemic anti-tumorimmune response capable of rejecting tumor cells at the site of thetreatment and throughout the body.

In an exemplary embodiment, the delivery of a biologically active smallmolecule was studied. In particular, the activity of thechemotherapeutic agent Cytoxan® delivered to the skin with CMCmicroneedle arrays was studied. The use of Cytoxan® enables directmeasurement of biologic activity (Cytoxan® induced apoptosis in theskin) with a representative of a class of agents with potential clinicalutility for the localized treatment of a range of cutaneousmalignancies.

To directly evaluate the immunogenicity of CMC microneedle arrayincorporated antigens, the well characterized model antigen ovalbuminwas used. Pyramidal arrays were fabricated incorporating either solubleovalbumin (sOVA), particulate ovalbumin (pOVA), or arrays containingboth pOVA along with CpGs. The adjuvant effects of CpGs are wellcharacterized in animal models, and their adjuvanticity in humans iscurrently being evaluated in clinical trials.

Immunization was achieved by applying antigen containing CMC-microneedlearrays to the ears of anesthetized mice using a spring-loaded applicatoras described above, followed by removal of the arrays 5 minutes afterapplication. These pyramidal microneedle arrays contained about 5 wt %OVA in CMC and about 0.075 wt % (20 μM) CpG. As a positive control, genegun based genetic immunization strategy using plasmid DNA encoding OVAwas used. Gene gun immunization is among the most potent andreproducible methods for the induction of CTL mediated immune responsesin murine models, suggesting its use as a “gold standard” for comparisonin these assays.

Mice were immunized, boosted one week later, and then assayed forOVA-specific CTL activity in vivo. Notably, immunization with arrayscontaining small quantities of OVA and CpG induced high levels of CTLactivity, similar to those observed by gene gun immunization (FIG. 27).Significant OVA-specific CTL activity was elicited even in the absenceof adjuvant, both with particulate and soluble array delivered OVAantigen. It is well established that similar responses requiresubstantially higher doses of antigen when delivered by traditionalneedle injection.

To evaluate the stability of fabricated arrays, batches of arrays werefabricated, stored, and then used over an extended period of time. Asshown in FIG. 28, no significant deterioration of immunogenicity wasobserved over storage periods spanning up to 80 days (longest time pointevaluated). Thus, the CMC microneedle arrays and this deliverytechnology can enable effective cutaneous delivery of antigen andadjuvants to elicit antigen specific immunity.

To evaluate the delivery of a biologically active small molecule,pyramidal CMC-microneedle arrays were fabricated with the low molecularweight chemotherapeutic agent Cytoxan® (cyclophosphamide), or withFluoresBrite green fluorescent particles as a control. Cytoxan® wasintegrated at a concentration of 5 mg/g of CMC, enabling delivery ofapproximately about 140 μg per array. This is a therapeutically relevantconcentration based on the area of skin targeted, yet well below levelsassociated with systemic toxicities. Living human skin organ cultureswere used to assess the cytotoxicty of Cytoxan®. Cytoxan® was deliveredby application of arrays to skin explants as we previously described.Arrays and residual material were removed 5 minutes after application,and after 72 hours of exposure, culture living skin explants werecryo-sectioned and fixed. Apoptosis was evaluated using greenfluorescent TUNEL assay (In Situ Cell Death Detection Kit, TMR Green,Roche, cat#:11-684-795-910). Fluorescent microscopic image analysis ofthe human skin sections revealed extensive apoptosis of epidermal cellsin Cytoxan® treated skin as shown in FIG. 29A. As shown in FIG. 29B, novisible apoptosis was observed in fluorescent particle treated skinthough these particles were evident, validating that the observed areawas accurately targeted by the microneedle array.

Direct Fabricated Microneedle Arrays

The micromilling of mastermolds described above allows the production ofmicroneedle arrays with a variety of geometries. In another embodiment,systems and methods are provided for fabricating a microneedle array bydirectly micromilling various materials, such as dried CMC sheets. Thesame general tooling that was described above with respect to themicromilling of mastermolds can be used to directly micromillingmicroneedle arrays.

Direct micromilling of microneedle arrays eliminates the need formolding steps and enables a simplified, scalable, and preciselyreproducible production strategy that will be compatible with largescale clinical use. Moreover, direct fabrication of the microneedlearrays through micromilling enables greater control of microneedlegeometries. For example, micromilling permits the inclusion ofmicroneedle retaining features such as undercuts and/or bevels, whichcannot be achieved using molding processes.

The reproducibility of direct milling of microneedle arrays isparticular beneficial. That is, in direct micromilling all of themicroneedles are identical as a result of the milling fabricationprocess. In molding operations, it is not uncommon for some needles tobe missing or broken from a given patch as a result of the process ofphysically separating them from the molds. For use in certain medicalapplications, the reproducibility of the amount of bioactive componentsin the array is very important to provide an appropriate level of“quality control” over the process, since irregularities in the needlesfrom patch to patch would likely result in variability in the dose ofdrug/vaccine delivered. Of course, reproducibility will also be animportant benefit to any application that requires FDA approval.Spincast/molded patches would require special processes to assureacceptable uniformity for consistent drug delivery. This quality controlwould also be likely to result in a certain percentage of the patches“failing” this release test, introducing waste into the productionprocess. Direct micromilling eliminates or at least significantlyreduces these potential problems.

Molding processes also have inherent limitations because of the need tobe able to fill a well or concavity and remove the cured molded partfrom that well or concavity. That is because of mold geometries,undercuts must generally be avoided when molding parts or the part willnot be removable from the mold. That is, a geometrical limitation of amolded part, such as a molded microneedle array, is that any featurelocated closer to the apex must be narrower than any feature locatedtoward the base.

Accordingly, in view of these limitations, FIG. 20 illustrates schematicrepresentation of microneedle shapes and structures that are generallysuitable for fabrication by molding. That is, the shapes and structuresshown in FIG. 20 do not contain any undercuts that would prevent thepart (i.e., the microneedles) from being removed from a production mold.In contrast, FIG. 30 illustrates a beveled, undercut microneedle shapethat cannot be molded in the manners described herein.

This geometry can only be created through direct fabrication using theproposed micromilling technology. The negative (bevel) angle facilitatesbetter retention of the microneedles in the tissue. In addition, becausethe microneedle of FIG. 30 has a wider intermediate portion (with alarger cross-sectional dimension) above a lower portion (with a smallercross-sectional dimension), a greater amount of the bioactive materialcan be delivered by configuring the microneedle to hold or store thebioactive material in the wider section, which is configured to beretained within the skin. Thus, the larger cross-sectional dimension ofthe intermediate portion can “carry” the bulk of the bioactivecomponent. Since the lower portion tapers to a narrower cross-sectionaldimension, the wider intermediate portion will obtain good penetrationfor delivery of the bioactive component into the skin layer. A portionabove the intermediate portion desirably narrows to a point tofacilitate entry of the microneedles into the skin layers.

Another limitation of molded parts is that it can be difficult toprecisely fill a very small section of a mold. Since production moldsfor microneedle arrays comprise numerous very small sections, it can bedifficult to accurately fill each well. This can be particularlyproblematic when the mold must be filled with different materials, suchas a material that contains a bioactive component and a material thatdoes not contain a bioactive component. Thus, if the production mold isto be filled with layers, it can be difficult to accurately fill thetiny wells that are associated with each microneedle. Suchreproducibility is particularly important, since the microneedles areintended to deliver one or more bioactive components. Thus, even slightvariations in the amounts of bioactive component used to fill productionmolds can be very undesirable.

Also, by using a lamination structure to form a sheet or block that canbe micromilled, various active components can be integrated into asingle microneedle by vertical layering. For example, in an exemplaryembodiment, CMC-hydrogel and CMC-sOVA-hydrogel (80% CMC/20 wt % OVA)were layered into the form of a sheet or block. This composite sheet canbe micro-machined using the direct micromilling techniques describedherein.

FIG. 31 is a stereo-microscopic image analysis of an entire microneedlearray. The microneedle comprises a 10×10 array of microneedles. FIG. 32is an enlarged segment of the microneedle array of FIG. 31. The layeringof two components is shown in FIG. 32, which illustrates darker areas ofthe microneedles at tip portions and lighter areas of the microneedlesat base portions. The darker layer at the tip represents the layercomprising a bioactive component, in this case soluble ovalbumincontained in a CMC layer.

Although the formation of a layer containing active material (e.g.,antigen) and the subsequent micromilling of the layer (and any otheradjacent layers) may require the use of relatively large amounts of theactive material, the material can be removed (e.g., in the form ofchips), recovered, and recycled. Direct machining technology is notrestricted by the geometrical constraints arising from themolding/de-molding approach, and thus, is capable of creating moreinnovative needle designs (e.g., FIG. 30), which can significantlyimprove the retained needle-volume and needle retention time in theskin.

The production of sheets or blocks by forming a plurality of layers canprovide a solid material that can be micro-machined and which cancomprise one or more layers with a bioactive component. For example, adissoluble solid carboxymethylcellulose polymer based block or sheetwith well-defined and controlled dimensions can be fabricated by alamination process. The resulting sheet or block can be fullymachineable, similar to the machining of plastic or metal sheets orblocks. As described herein, the fabrication process can be suitable forthe incorporation of bioactive components into the matrix withoutsignificantly reducing their activity levels.

As described below, a fabricated sheet of material (such as a CMC basedmaterial) can be directly micro-machined/micromilled) to produce one ormore microneedle arrays suitable for delivering active ingredientsthrough the skin. This dissoluble biocompatible CMC block-material canbe used for the delivery of soluble or insoluble and particulate agentsin a time release manner for body surface application.

The biocompatible material can be suitable for implants in deeper softor hard tissue when dissolution of the scaffolding material is requiredand useful.

The following method can be used to prepare a carboxymethylcellulose(CMC) polymer low viscosity hydrogel to 12.5% concentration. The 12.5%carboxymethylcellulose (CMC) low viscosity hydrogel can be prepared inwater or other biocompatible buffer, such as (but not limited to) PBS orHBS. During the preparation of the polymer solution, soluble agents(such as nucleic acid, peptides, proteins, lipids or other organic andinorganic biologically active components) and particulates can be added(e.g. ovalbumin, a soluble agent). Ferrous particulates carrying activeingredients at 20 w/w % of CMC can be used.

The preparation of 1000 g sterile 12.5% CMC hydrogel with no activecomponent can be achieved as follows:

1) Measure 125 g CMC, add 875 g water or other water based solvent.

2) Stir to homogeneity in overhead mixer.

3) Autoclave homogenate to sterility at 121 degrees Celsius for 1 hour(the autoclaving step can reduce viscosity for improved layering)

4) Cool to 22 degrees Celsius.

5) Vacuum treat the resulting material at 10 torr and 22 degrees Celsiusfor 1 hour to remove trapped micro-bubbles.

6) Centrifuge product at 25,000 g for 1 hour in vacuum chamberedcentrifuge (for floating and further removing residual micro bubbles).

7) Store the CMC-hydrogel product at 4 degrees Celsius.

The preparation of 1000 g sterile 12.5 w/w % dry content 20/80%ovalbumin/CMC hydrogel can be achieved as follows:

1) Measure 100 g CMC add 650 g water or other water based solvent.

2) Stir to homogeneity in overhead mixer.

3) Autoclave homogenate to sterility at 121 degrees Celsius for 1 hour(this autoclaving step can reduce viscosity for improved layering).

4) Cool to 22 degrees Celsius.

5a) Dissolve 25 g ovalbumin in 225 g water.

5b) Sterile filter ovalbumin solution on 0.22 μm pore sized filter.

6) Mix to homogeneity, under sterile conditions the 750 g CMC hydrogelwith 250 g sterile ovalbumin solution.

7) Vacuum treat the resulting material at 10 torr and 22 degrees Celsiusfor 1 hour to remove trapped micro-bubbles.

8) Centrifuge product at 25,000 g for 1 hour in vacuum chamberedcentrifuge (for floating and further removing residual micro bubbles).

9) Store the CMC-hydrogel product at 4 degrees Celsius.

The preparation of 100 g sterile 12.5 w/w % dry content 20/80%particulate-ovalbumin/CMC hydrogel can be achieved as follows:

1) Measure 10 g CMC add 87.5 g water or other water based solvent.

2) Stir to homogeneity in overhead mixer.

3) Autoclave homogenate to sterility at 121 degrees Celsius for 1 hour(this autoclaving step can reduce viscosity for improved layering).

4) Cool to 22 degrees Celsius.

5) Disperse 2.5 g particulate-ovalbumin in the 97.5 g, 22 degreesCelsius CMC-hydrogel and mix to homogeneity, under sterile conditions.

6) Vacuum treat the resulting material at 10 torr and 22 degrees Celsiusfor 2 hour to remove trapped micro-bubbles.

7) Centrifuge product at 3,000 g for 1 hour in vacuum chamberedcentrifuge (for floating and further removing residual micro bubbles).

8) Store the CMC-hydrogel product at 4 degrees Celsius.

Note in this example, particulate-ovalbumin is prepared from activatediron beads reaction to ovalbumin. However, it should be noted that theabove descriptions are only exemplary embodiments and other compoundsand active ingredients can be used.

A solid block/sheet carboxymethylcellulose (CMC) can be fabricated inthe following manner using the low viscosity CMC-hydrogels describedabove.

The fabrication process can comprise a laminar spreading of the polymerat a defined thickness and a drying of the layered polymer to less thanabout 5% water content using sterile dried air flow over the surface ofthe polymer layer. The above two acts can repeated until the desiredblock thickness is achieved.

A method of performing a laminar CMC-hydrogel layering of a definedthickness over the casting mold assembly is described with reference toFIG. 33. FIG. 33 illustrates a cross-sectional view of the casting-moldassembly which includes: (a) casting bed; (b) adjustable casting bedwall; (c) casting-bed depth adjustment assembly; and (d) an acrylicspreader. It should be noted that FIG. 33 is not drawn to scale orotherwise shown with elements in their proper proportions.

The casting mold assembly can be constructed from acrylic (Plexiglas)and can comprise a casting bed base unit, a vertically adjustablehydrophobic casting-bed wall, and a casting-bed adjustment mechanism.The casting bed base unit (a1) can include a removable/replaceablecasting bed top plate (a2) with an attached cellulose layer (a3). Thecellulose layer can be about 0.5 mm in thickness. The verticallyadjustable hydrophobic casting-bed wall (b) can be adjusted using thecasting-bed depth adjustment mechanism, which can be comprised oflead-screw (c1) and level adjustment knob (c2). In the illustratedembodiment, a quarter turn of this knob can result in a 0.5 mm lift ofthe bed wall.

Initially, the adjustable casting bed wall can be set to height wherethe distance between the acrylic spreader and the cellulose layer of thebed is about 1 mm when the spreader is in position. A predefined volume(e.g., about 0.1 ml/cm2) of the 12.5% CMC-hydrogel can be added andlayered. The layer can be evened or leveled by sliding the acrylicspreader (d) on the top surface of the adjustable casting wall to yieldan even layer of about 1 mm of CMC-hydrogel. The layered CMC-hydrogelcan be dried to a solid phase in the drying apparatus shown in FIG. 34and described in more detail below.

The layering and drying steps can be repeated until the desired layeredstructure (sheet) is achieved. The casting bed wall can be raised by anappropriate amount during the addition of each layer. For example, afteradding each layer, the bed wall can be raised or lifted by about 0.5 mm.Thus, the above-described cycle can deposit about 0.5 mm solid CMClayer. The process (e.g., the layering of material, the raising of bedwall, etc.) can be repeated until the desired block thickness achieved.

The layered CMC-hydrogel polymer can be dried in various manners. Forexample, FIG. 34 illustrates a drying apparatus that can be used to drythe various deposited layers of the sheet material. It should be notedthat FIG. 34 is not drawn to scale or otherwise shown with elements intheir proper proportions. A fan can provide continuous gas flow (e.g.,air or other inert gas, such as nitrogen) over the CMC-hydrogel layeredin the casting mold assembly. The gas flow will result in a gentledehydration of the CMC-hydrogel layer. The drying speed can be adjustedto prevent or reduce gas enclosures (e.g., air bubbles) in the solid CMCproduct. The humid air over the layer can be dried over desiccant (e.g.,an air dryer or dehumidifier), temperature adjusted, and returned overthe hydrogel again by the speed-controlled fan. A hygrometer can bepositioned on the humid side of the chamber to provide an indication ofthe status of the drying process. After a predetermined dryness has beenachieved, as indicated by the hygrometer, the drying process can beended.

Airflow can be adjusted to affect the drying speed. In the exemplaryembodiment, the airflow is controlled to be between about 0.1-2.0 m/sec;the temperature is between ambient and about 50 degrees Celsius. Usingthese configurations, the drying time of a single layer CMC-hydrogel canbe about 0.5-4 hours depend on the airflow and the set temperature.

The pure CMC based product can be transparent, light off white, or ambercolored. Its specific gravity can be about 1.55-1.58 g/ml. The productis desirably free of micro-bubbles and otherwise suitable forfabricating micron scale objects. The physical characterization of thefinal block/sheet product (hardness, tensile strength, etc.) can vary,but should generally be able to resist physical stresses associated withmicromilling.

As described above, the microneedle arrays disclosed herein are capableof providing reliable and accurate delivery methods for variousbioactive components. The structural, manufacturing, and distributionadvantages characteristic of the above-described microneedle arrays canbe particularly applicable for use in delivering vaccines. Advantages ofthese microneedle arrays include (1) safety, obviating the use ofneedles or living vectors for vaccine delivery, (2) economy, due toinexpensive production, product stability, and ease of distribution, and3) diversity, via a delivery platform compatible with diverse antigenand adjuvant formulations.

Moreover, cutaneous immunization by microneedle array has importantadvantages in immunogenicity. The skin is rich in readily accessibledendritic cells (DCs), and has long been regarded as a highlyimmunogenic target for vaccine delivery. These dendritic cellpopulations constitute the most powerful antigen presenting cells (APCs)identified thus far. For example, genetic immunization of skin resultsin transfection and activation of dendritic cells in murine and humanskin, and these transfected dendritic cells synthesize transgenicantigens, migrate to skin draining lymph nodes, and efficiently presentthem through the MHC class I restricted pathway to stimulate CD8+T-cells. The immune responses induced by skin derived DCs are remarkablypotent and long-lasting compared to those induced by other immunizationapproaches. Recent clinical studies demonstrate that even conventionalvaccines are significantly more potent when delivered intradermally,rather than by standard intramuscular needle injection. Thus,microneedle arrays can efficiently and simultaneously deliver bothantigens and adjuvants, enabling both the targeting of DCs and adjuvantengineering of the immune response using the same delivery platform.

High Frequency Electro-magnetic Oscillating Applicator

Microneedle array devices can be applied to human skin by a variety ofmethods including self or assisted application by human pressure (e.g.,pushing with a finger or thumb), or with spring-loaded devices. Tofacilitate the ease and reproducibility of delivery of microneedle arraydevices, including tip-loaded microneedle arrays, an applicator deviceis described herein. The applicator device is configured to convert highfrequency electromagnetic oscillation into unidirectional mechanicalresonance of the active head. This in turn enables multiple reproduciblelow amplitude and high frequency pressure strokes that facilitateinsertion of the microneedles of microneedle arrays into tissuesincluding human skin.

As shown in FIG. 38, the applicator can comprise an applicator head, anoscillator-energy converter, an electro-magnetic oscillator, and a powersource. If desired, one, or all of these four elements can be detachablefrom the applicator device.

An applicator head can be interchangeable to accommodate and act ondifferent sized and shaped tissue surface areas. As shown in FIG. 39,various applicator head geometries can be utilized in combination withthe applicator described herein. Applicator heads are interchangeablemade of stainless steel or other chemically and physically resistantmaterials. If desired, the applicator heads can be autoclaved forsterility and/or sterilized by alcohols or other chemicals.Alternatively, or in addition, gas sterilization (ethylene oxide) ispossible.

Application specific geometries can be rapidly designed and fabricated.For example, the area of a single application in this example can rangefrom 5 mm² to 250 mm² dependent on the active head's geometry. A broaderrange can be achieved by simple structural variation of the head'sgeometry.

The oscillator energy converter unit can be configured to transforms theelectro-magnetic oscillation into mechanical movements of the applicatorhead. The amplitude of the applicator head's in direction Z can becontrolled between 0.5-2.5 mm (FIG. 40; A). In some embodiments, headmovements in direction X-Y can be configured to be negligible, <0.2 mm(FIG. 40; B). The frequency of the mechanical movements resulting fromthe energy conversion in the direction Z can be controlled between500-25000 rpm. If desired, the oscillator energy converter unit can bedetachable and can be disposed or sterilized as needed.

The electro-magnetic (EM) oscillator can be composed of three subunits.These subunits can include a (1) regulated power supply generating thevoltage and power for the controller and high frequency EM oscillator; a(2) controller-regulator generates the high frequency signal and therequired current for the EM oscillator; and (3) an EM oscillator. Theoutput frequency can be controlled by the user (e.g., in ranges such asfrom 100-500 Hz). In some embodiments, the EM oscillator can be fullyenclosed and can be sterilized by alcohol solutions or other chemicalagents.

The power source unit can also be detachable to accommodate differentattachable power sources such as:

a. Battery, regular disposable alkaline or any other type.

b. Rechargeable NiCad or Li oxide battery with built in inductivecharger.

c. Electronic power adapter to 100-240 V

The applicator can provide several benefits in connection withmicroneedle array application. For example, the applicator canminimalize the mechanical force needed for microneedle array insertioninto tissues. The applicator can also reduce pain effects compared toexisting spring-loaded applicators. In addition, the applicator can beportable and the components of the applicator can be detachable andinterchangeable. Finally, the applicator can be configured so that it iscapable of being sterilized for aseptic use.

In view of the many possible embodiments to which the principles of thedisclosed embodiments may be applied, it should be recognized that theillustrated embodiments are only preferred examples and should not betaken as limiting the scope of protection. Rather, the scope of theprotection is defined by the following claims. We therefore claim allthat comes within the scope and spirit of these claims.

We claim:
 1. A dissolvable microneedle array for transdermal insertioninto a patient comprising: one or more bioactive components; a baseportion; and a plurality of microneedles extending from the baseportion, the plurality of microneedles comprising a top half and abottom half wherein the one or more bioactive components areconcentrated in the top half of the microneedles, wherein the baseportion and the plurality of microneedles comprise a plurality of layersof dissoluble biocompatible material, wherein the dissolublebiocompatible material define a shape of the plurality of microneedles,the one or more bioactive components are contained in the plurality oflayers, and at least some of the plurality of layers that contain theone or more bioactive components are spatially separated from others ofthe plurality of layers that contain the one or more bioactivecomponents.
 2. The dissolvable microneedle array of claim 1, wherein thebase portion is substantially formed without any bioactive componentscontained therein.
 3. The dissolvable microneedle array of claim 2,wherein the plurality of microneedles have a first cross-sectionaldimension at an area of a top portion, a second cross-sectionaldimension at an area of a bottom portion, and a third cross-sectionaldimension at an area of an intermediate portion, wherein the thirdcross-sectional dimension is greater than the first and secondcross-sectional dimensions.
 4. The dissolvable microneedle array ofclaim 3, wherein each microneedle generally tapers to a point above theintermediate portion and each microneedle generally tapers to a smallercross-sectional dimension below the intermediate portion.
 5. Thedissolvable microneedle array of claim 1, wherein the dissolublebiocompatible material is carboxymethylcellulose.
 6. The dissolvablemicroneedle array of claim 2, wherein the one or more bioactivecomponent comprises at least two different bioactive components.
 7. Thedissolvable microneedle array of claim 6, wherein the at least twodifferent bioactive components are selected from the group consisting ofa chemotherapeutic agent, an adjuvant, and a chemo attractant for acancer chemo immunotherapy application.
 8. The dissolvable microneedlearray of claim 6, wherein the one or more bioactive component comprisesan antigen and an adjuvant for a vaccine application.
 9. The dissolvablemicroneedle array of claim 2, wherein the one or more bioactivecomponent comprises at least one viral vector.
 10. The dissolvablemicroneedle array of claim 9, wherein the at least one viral vectorcomprises an adenovector.
 11. The dissolvable microneedle array of claim1, wherein the one or more bioactive component comprises doxorubicin.12. The dissolvable microneedle array of claim 1, wherein the spatiallyseparated layers of the one or more bioactive components comprisedifferent active components.
 13. The dissolvable microneedle array ofclaim 1, wherein the spatially separated layers of the one or morebioactive components comprise different amounts of the same bioactivecomponent.
 14. The dissolvable microneedle array of claim 1, wherein thespatially separated layers of the one or more bioactive componentscomprise different concentrations of the same bioactive component.